New motherboard

Hi - I'm getting my friendly computer shop to install a new motherboard, processor and memory. They're going to do all the necessary work to get it up and running again (I hope!) but is there anything I ought to know beforehand? For instance, I've got Acronis TI - is this any good for recreating whatever it's got backed up, or do I forget everything, give them a copy of a Belarc report and let them get on with it?

Do I need to back up my own data or can that be picked up from Acronis? I've never had to use it, and am a bit confused by the manual. Or can I put all my data on my USB external hard drive and will it work without any problems?

Bit of a 'how long is a piece of string' question, I suspect, but I don't really know what I need to know!